Along with development of display technology, displays with better image quality, richer color effect and better performance are continually developed. In recent years, a three-dimensional (3D) display technique has a development trend from cinema applications towards home applications. Since a key of the 3D display technique is to ensure a left eye and a right eye of a user to respectively view a left eye image and a right eye image of different viewing angles, according to the current 3D display technique, the user generally wears a pair of special glasses to filter the left eye images and the right eye images.
It is inconvenient for a user wearing the special glasses, especially for those wearing near-sighted or far-sighted glasses, it is inconvenient and uncomfortable to wear an extra pair of special glasses. Therefore, a naked-eye 3D display technique becomes one of research and development emphasises. A naked-eye 3D display is adapted to produce a plurality of viewing zones in space, and display images of different viewing angles in different viewing zones. When the left eye and the right eye of the user are respectively located at two adjacent viewing zones, the user can view images of two different viewing angles. In this way, the images of the two different viewing angles are combined in user's brain to form a 3D image.
However, the above situation is achieved when the user is located near an optimal viewing distance of the naked-eye 3D display. When the user views the naked-eye 3D display in a distance too longer than or too shorter than the optimal viewing distance, besides a poor image quality or a blurred image is probably obtained, incorrect brightness, contrast and images also probably occur, and the user's eyes may have an uncomfortable feeling. Therefore, it is an important issue of the 3D display technique to correctly find the optimal viewing distance of the naked-eye 3D display.